Method and means for simultaneously testing and filtering solutions



Patented Mar. 23, 1943 METHOD sun MEANS FOR SIMULTANEOUS- LY 'ras'rmc. Arm mraamc SOLUTIONS Raymond B. Goodale, Worcester, Mass.

No lilrawing. Application July 3, 1940, Serial No. 343,833

7 Claims. (Cl. 23-230) This invention relates to a method and means for determining by precipitation the presence of a given substance in. a solution being tested. The invention will be illustrated in connection with urinalysis for albumin, but I do not wish to limit the broad scope of my invention to that particular procedure.

Heretofore. all known methods of determining the presence of albumin in urine have required at least two steps, first, the addition of an acid, as acetic, to hold the phosphates in solution, or filtering to remove debris such as pus cells, and second, the addition of an acid to coagulate or precipitate the albumin. In hospital laboratories where many tests are made each day, and in the physicians office when the patient waits for the result of the test, these steps consume much time. It is an important object of my invention to impregnate a filter paper with an acid which will precipitate the albumin, such as sulphosalicylic acid, and pour the urine as received from the patient into the folded filter paper. If a1- bumin is present it will appear as a cloud in the filtrate. The filter paper is prepared in quantity and dried to be ready for use when needed. The water in the urine dissolves the acid crystals when passing through the paper and little if any of the albumin is precipitated above and held back by the paper.

Paper treated with sulphosalicylic acid has a tendency, after long standing, to crack when folded, due probably to the action of, the acid on the cellulose of the paper. It is a further object of my invention to add to the acid an ingredient which will counteract the cracking effect which the acid has on the paper. For this purpose I have successfully used glycerine which permits the paper to be used satisfactorily for a considerable period of time after preparation.-

The foregoing sets forth the general objects of my invention, but other and detailed objects will appear hereinafter.

In carrying my invention into eflect I employ any of the standard filter papers, such for instance, as the four inch No. 201 made by Reeve Angel and Co. This is a smooth paper and I prefer it to the rough papers. These papers are available commercially in packages of one hundred each enclosed in a wrapper. The papers are immersed in a vat containing a 10% solution of sulphosalicylic acid to which has been added the desired amount of glycerine. The papers remain in the solution until impregnation is completed, after which the papers are removed and spread out separately to dry at room temperatures on any surface which will not absorb too much of to allow the drippings to fall into the vessel.

When the excess solution has drained away, the papers are separated and laid out flat to dry. When dried the filter papers are ready for use.

When a test is to be made the paper is folded in the usual way, that is, first along a diameter and then at right angles to the diameter to form four quadrants. The paper is then opened to form an inverted cone and placed in the usual glass cup. A funnel may be used, but is not necessary. The urine to be tested is then poured into the paper as received from the patient and without preliminary treatment of any. kind. Solids in suspension are held back by the paper and the liquid part of the urine dissolves the sulphosalicylic acid crystals when passing through the paper. If albumin is present it will coagulate to form a cloud in the filtrate in the cup. The extent of the cloud is an approximate quantitative indication of the amount of albumin present in the urine. This single operation, therefore, holds back the solidswhich would give a false visual indication if allowed to pass into the cup-and at the same time dissolves the acid crystals to coagulate the albumin in the filtrate.

While I have mentioned sulphosalicylic acid specifically for determining albumin in urine, I do not wish to be limited to this reagent. Other acids may be used, such for instance,'as tannic or phosphotungstic acids. Sulphosalicylic acid, however, gives a stronger reaction than tannic acid and is less expensivethan phosphotungstic acid, and it is preferred for these reasons.

The procedure already outlined is a specific example of the more general subject matter of my invention. Considered in its broader aspects my invention provides a simplified procedure by which a liquid A containing a solution B and a precipitate C can be filtered to hold back 0 and at the same time precipitate an ingredient D held in solution in B by means of a reagent E on the filter paper, the reagent being dissolved by B when passing through the paper and thus enabled to act on D. The reagent E is prevented from cracking the paper by a preventive agent F, glycerine in the example already given, which does not interfere with the interaction between reagent E and ingredient D.

From the foregoing it will be seen that I have provided a simple means for simultaneously separating a liquid from its solids and precipitating an ingredient of the liquid. The paper and method are particularly useful in urine analysis.

What I claim is:

1. A filter paper for the determination of albumin in urine comprising a body of porous paper impregnated with sulphosalicylic acid and dried.

2. A filter paper for the determination of albumin in urine comprising a body of porous dry paper impregnated with an acid soluble in urine and which when added to urine containing alburain will precipitate the albumin. 7

f 3. A filter-paper tor the determination of alg'bumin in urine comprising a body of porous paper fimpregnated with sulphosalicylic acid and glycerine and dried.

v-i=. The method of qualitatively determining the presence of albumin inurine which consists in the following steps: impregnating a porous filter paper with sulphosalicylic acid, drying the paper, passing the untreated urine as received from the patient through the paper to hold back solid debris in the urine, and examining the liquid which passes through the paper for coas ated albumin.

5. The method of qualitatively determining the presence of albumin in urine which consists in the following steps: impregnating a porous filter paper with an albumin precipitating reagent soiuble in urine, drying the paper, passing the untreated urine as received from the patient through the paper to hold back solid debris in the urine, and examining the liquid which passes through the paper for coagulated albumin.

6. A filter paper for the determination of albumin in urine comprising a body or porous paper which has been moistened with a solution containing approximately 10% of sulphosalicylic acid and dried.

7. A filter paper for the determination of albumin in urine comprising a body of porous paper which has been saturated in a solution containing approximately 9% of sulphosalicylic acid, 14% of glycerine and 77% of water and dried.

RAYMOND H. GOODALE. 

